The invention generally relates to methods for manufacturing a semiconductor device with improved device performance, and more particularly to methods for manufacturing semiconductor devices by imposing tensile and compressive stresses in the substrate.
Mechanical stresses (e.g., tensile stress and compressive stress) within a semiconductor substrate can modulate device performance, which means stresses within a semiconductor substrate enhance semiconductor device characteristics. Thus, the characteristics of a semiconductor device can be improved by creating tensile and/or compressive stresses in the channel regions of an N type device (e.g., NFET) and/or a P type device (e.g., PFET). However, the same stress component, either tensile or compressive stress, discriminatively affects the characteristics of an N type device and a P type device. For example, when tensile stress is applied to a device in the direction of current flow, the performance of an N type device is enhanced but the performance of a P type device is degraded. Thus, in order to maximize the performance of both N type and P type devices formed on the same semiconductor substrate, each stress component should be selectively engineered and applied to either NFETs or PFETs.
To selectively create tensile stress to an N type device and compressive stress to a P type device, respectively, distinctive processes and different combinations of materials are used. For example, a trench isolation structure can be used in forming N type and P type devices. When the trench isolation structure is formed, an isolation region for the N type device contains the isolation material which applies appropriate stress to the N type device in a longitudinal direction and in a transverse direction. Further, the first isolation region and the second isolation region are provided for the P type, which apply a unique mechanical stress on the P type device in the longitudinal direction.
Alternatively, liners can be formed on the side surfaces of a gate electrode, to selectively induce appropriate stress types in the channels of the N type or P type devices. By providing liners, it is possible to apply appropriate stress closer to the device than relying on the trench isolation fill technique.
While these methods enables selectively applying tensile stress to the N type device and compressive stress to the PFET device along the longitudinal direction, they require more complicated processing steps and specific materials, thereby increasing manufacturing costs. Further, only a moderate amount of stress is obtained, such as only in the order of hundreds of MPa.
Therefore, there is a need for more cost-effective and cost-effective methodology for creating larger amount s of tensile and compressive stresses for both N type and P type devices without departing from readily available processing techniques.